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Re: [libvirt] [PATCH] move ebiptables script out of /tmp



On 06/16/2010 01:11 PM, Stefan Berger wrote:
> On 06/16/2010 02:54 PM, Jamie Strandboge wrote:
>> Hi,
>>
>> I noticed today that ebiptablesWriteToTempFile() creates a temporary
>> file in /tmp that is later executed. It uses mkstemp() and therefore is
>> safe from symlinks attacks, however, there is not really any reason that
>> I can see why it is using /tmp instead of somewhere
>> like /var/lib/libvirt. If libvirtd is confined under a MAC which allows
>> execution of /tmp/virtd* and a vulnerability is found in libvirtd,
>> the /tmp path leaves an opportunity for a local non-root attacker to
>> write a script in /tmp and then subvert libvirt to execute that script.
>>    
> I don't mind the move of the temporary file, but I'd like to understand
> how would someone subvert libvirt to run an arbitrary script?

I'm with Stefan - the whole point of mkstemp is that the created file
has 0600 permissions, and /tmp is restricted-deletion, so no other user
can either overwrite the file contents or unlink it and replace it with
an alternate file.  Then again, gnulib documents that glibc 2.0.7 or
older would create a file with group/other permissions if the umask
wasn't set prior to the mkstemp() call, and gnulib's mkstemp() does not
work around this issue; but that's a rather old version of glibc to be
worrying about.

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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